Dry-copying method for producing flat, individually dosed preparations of active agents

ABSTRACT

A method for metering active ingredient in powder form onto a predetermined area is characterized in that  
     the active ingredient is transferred as electrically charged powder to a roll with the opposite charge,  
     the active ingredient transferred to the roll is transferred to a two-dimensional substrate with an electric charge opposite to the active ingredient,  
     the active ingredient transferred to the substrate is fixed by means of a heat treatment.

[0001] Single-dose active ingredient preparations mean preparations which contain a predetermined amount of active substance in separate preparation units which can be handled individually.

[0002] An active ingredient for the purpose of this invention may be understood to be, for example, a medicinal substance, an insecticide, a pesticide, a reagent, etc.

[0003] If an active substance means, for example, a medical active ingredient, such single-dose pharmaceutical forms are, for example, tablets, capsules, suppositories or transdermal therapeutic systems (TTS).

[0004] Non-single-dose pharmaceutical forms would be, for example, sprays, syrups, ointments and drops, with which the actual dosage takes place only immediately before use.

[0005] In single-dose active ingredient preparations, the active ingredient is to be processed in an appropriate amount together with any excipients necessary to give the active ingredient preparations ready for use. This technology can be regarded as mature for the production of tablets and capsules. Modern tablet presses and capsule-filling machines guarantee a high production rate and very accurate metering in the range 95-105% of the specification.

[0006] Transdermal therapeutic systems are still a relatively recent pharmaceutical form which is used externally in the form of a plaster on the skin and delivers the active ingredient through the skin to the body. Special metering techniques are used to produce these TTS, and further innovations in terms of new metering techniques are possible.

[0007] In one embodiment of these TTS, the active ingredient is contained directly in the adhesive and, during production, is metered together with the adhesive two-dimensionally onto a sheet.

[0008] This means that TTS are the only pharmaceutical form for which it is important to meter a medicinal active ingredient onto a predetermined area in a predetermined amount. Considering non-medicinal active ingredients such as, for example, insecticides, pesticides or reagents, two-dimensional preparations in the form of impregnated papers, sheets or boards have been known for a long time. However, the demands on the accuracy of metering in the area for these applications are not great.

[0009] The present invention is based on the object of providing a method for metering active ingredients in powder form onto a predetermined area.

[0010] This object is achieved with use of the techniques known from the dry copying process by a method according to the features of main claim 1.

[0011] It has emerged that this technique is capable of metering active ingredients in powder form onto an area with an accuracy sufficient for medicinal products. This is directly discernible with color copying, in which each color is metered separately, and major inaccuracies would result in wrong colors.

[0012] The dry copying process or xerography functions in the manner described hereinafter.

[0013] A roll coated with a photoconductive material is provided with a positive electric charge and exposed through a suitable optical system to the original to be copied. Through this procedure, the charge is at least partially removed wherever the conductivity of the photoconductive material increases due to the exposure.

[0014] In a next step, negatively charged colored particles (toners) are applied to the roll, but these remain adherent only on the still charged areas of the roll in an amount depending on the size of the charge, and produce a visible image there.

[0015] Subsequently, the colored particles-(toners) are transferred to a positively charged paper or sheet and fixed there by a heat treatment.

[0016] A modern variant of the method is employed in so-called laser printers. In this case, the roll is directly exposed to a laser beam without original, and thus the image is traced under computer control directly on the roll. Otherwise, the same technology is used for laser printers as for dry copiers.

[0017] The present invention is based on the use of these processes in order to transfer active ingredient particles, instead of the colored pigments, to paper or, in general, sheets.

[0018] Experiments were carried out with a normal black/white copier to find the amounts of toner which can be transferred to sheet and the reproducibility thereof.

[0019] Commercially available large polyester overhead sheets in the DIN A4 format are used as sheet. The original used was a dead-black sheet of paper, and the maximum degree of blackening was chosen for the copy. The results are recorded the following table. TABLE 1 Toner application Experiment number (mg/cm²) 1 0.609 2 0.601 3 0.640 4 0.603 5 0.603 6 0.604 Average 0.610 Rel. error (%) 2.4

[0020] The results show that-although only a comparatively small amount of toner was transferred, this was with an accuracy suitable for medicinal applications, too.

[0021] In another experiment it was then found whether the amount can be eased by multiple metering.

[0022] The results are depicted in FIG. 1 and show that the transferred amount of toner is proportional to the number procedures.

[0023] This result shows that although the amount transferred in one copying process is small, this disadvantage can be overcome by multiple copying without the accuracy of metering suffering thereby.

[0024] The amount of toner or active ingredient transferred depends on the charged state of the copying roll and can be increased by applying a stronger charge than usual with copying machines.

[0025] If the active ingredient is metered without a special pattern, it is possible to dispense entirely with the exposure step. In this case, the copying roll does not have to consist of photoconductive material.

[0026] If the metering is to take place in a pattern, the exposure step and the use of a copying roll coated with a photoconductive material, for example selenium, is necessary. The exposure can in this case take place via an original or else via a laser with computer control. The variability is, of course, greatest with computer-controlled laser exposure.

[0027] It is to be assumed that most active ingredients are colorless. From this viewpoint, it is worthwhile to admix an indicator dye to the active ingredient and excipient mixture in powder form. This dye then permits, after appropriate calibration, direct measurement by optical methods of the amount of active ingredient transferred, and automatic correction of any deviations from the specification.

[0028] The flat substrate onto which the active ingredient is transferred can moreover consist in principle of any materials as' long as it is flexible and suitable for withstanding the fixing procedure. It is conceivable in this connection that the material will be employed in the form of sheets or will be supplied from a roll. This material is then cut into smaller pieces during further processing and thus converted into the single-dose active ingredient preparation. An alternative possibility is for the material also to be perforated, in which case the dosage is predetermined by the perforation. 

1. Method for metering active ingredient in powder form onto a predetermined area, characterized in that the active ingredient is transferred as electrically charged powder to a roll with the opposite charge, the active ingredient transferred to the roll is transferred to a two-dimensional substrate with an electric charge opposite to the active ingredient, the active ingredient transferred to the substrate is fixed by means of a heat treatment.
 2. Method according to claim 1, characterized in that excipients likewise in powder form are metered together with the active ingredient.
 3. Method according to claim 2, characterized in that at least one excipient acts as fixative.
 4. Method according to claim 2, characterized in that one excipient is coloured and is used for optical determination of the amount of active ingredient.
 5. Method according to claims 1 to 4, characterized in that the roll is coated with a photoconducting material.
 6. Method according to claim 1, characterized in that the charge on the roll and thus the amount and/or the pattern of active ingredient transfer is influenced by exposure of the loaded roll.
 7. Method according to claim 6, characterized in that the exposure of the roll takes place via a computer-controlled laser or conventionally via the optical imaging of an original. 